Final answer:
The best observation describing an extensive property of table salt is the increase in electrical charge with more dissolved salt, as extensive properties depend on the substance's quantity. The correct option is C. The more salt that is dissolved in water, the greater the electrical charge
Step-by-step explanation:
The observation that best describes an extensive property of table salt is "The more salt that is dissolved in water, the greater the electrical charge". Extensive properties depend on the amount of substance present. The increase in the electrical charge is a reflection of the increased amount of dissolved salt, which corresponds to a higher number of ions in solution. This is contrasted with intensive properties, such as melting point and density, which do not change with the amount of the substance.